Sucker rod



Patented Mar. l5, 1932 AIBED Q'IORI'STLOVISLO; onNWlA'R/x, NEWLJEn-snx, AssIGNoR 'roi'ininnnnlrri. 4

frHnEAnLocx oonronarrom or ,NEW- YORK, No Y., 5A: CORPORATION or; .DELAWARE l This: invention relates to 'improvements 'in sucker rods l:forv oil Well umps and 'the' like.

The invenion' has -for its' l'principal objects to provide i. a* sectional A`s11cl{e1\rod of?" less Weight perunit of length, oeringfless'obstruction tovthe oil lowy and'less resistance" to reciprocation of therodin'the well tubing than i standard sucker rods now in .use and* use and which areytlie-` principal sources lofl the frequent breakage oft-he present" standard; sucker rods and to provide `'such' arod Where- "in the parts'or'sections' are thread coupled 'in such manner as to prevent accidental*un screwing of the parts Which'is a `frequent source of trouble With the-presentr standard rods." -1 r f1' lQtlierfobjectsof'the invention areto provide an efficient streamlined vsucker rodi'compris-v ing thread coupled section'sfself-held against i l rod. 'It'fwill be noted, however,V that the lrod` sections while havingabox atone' end do accidental?- disconnectionj; toV providef a sucker rod *comprising thread coupled: sections` of small diameter through-the --joints and wherein" the-mas's'of A"metal at 'the joints is much less than instandard sucker yrodjoints'; Lto provide a screw joint for sucker-rodmembers vso constructed! as toV substantially reduce the weightv 'and'rigidi'ty of the rod in the joint and throw the' vbending stresse/s 1into the" rod be-y yond the joints in suchmanner as to substanf tially eliminate 'li'abi-lityof breakage ofthe rod inthethreadedjoint; toprovi'de a selflockingithread joint vfor suckerrods wherein` the jointI is so constructed 'as toinc'rea'sethe factor' of safety of the rod with respect 'to axialload resistance;,ito'rprovide a thread jointed sucker rodiwherein abruptfchanges' of section-fandI concentration otbrea'kingv stresses' arel avoided'in all'pa'its''of the rod; f to provide a sectional thread-jointed? s'u'cker rodall partsof which have substanti'allythe'vr same areal in cross-section at all: vpoints-' 'in i' vtheir length-gend to provide a thread coupled`v` sucker rod-*joint wherein the externally vthreaded end or ends of each rod se'ction'are formed Without the'iisualeollar,'shoulde`r :and j pin portions. I U l A. f

The preferredembodinient ofthe invention -is' illustrated inf the accompanying drawings in which into the vvellg'f` Fig. 2' is a` View on an enlarged scale,partly `v in" 'central longitudinal section, 'through Vthel joint between twolike sectionsof the rodwi'th the part-s fullj7 coupled;`

Fig. 3 a-view similarto Fig'. 2 showing theparts ypartly coupled, `Ajust priorlto the lockl.` ing displacement between the ycoupling" threads l; and f Fig.' l4 al transverse? sectional' view' onfth'e line 4 4 of Fig. 1.

The particular vsucker rod shown is'- some- Whaty similar "to 'the'fsinglepin and box 'type of= sucker rodl lin that yitvv consists of likefsec l tions 'each externally threadedatV one I-end' andjhaving*anfinternally threaded box atits opposite end'to receive the externally thread-y ed lower endfofthe nexty above section ofthe not have the `usualcollar and. threaded'pin lower endofethe section as the rod is'assemr` f bledin"A the Well` and that' theusual abrupt box shoulder'isfalso omitted. 1 f

*The rod consists of like rod `sections 10 each hereinafter setv forth`each rod section" has a;

circular cross-sectioniof constant' diameter f f from end to end.' bln-Fig. 11,5W'here1n 1s illus- Fig: ris a fragmentary Side-elevadores the rodin the position 'in Which'it extendsv 15 at the' opposite end1,but`sin1`ply carry fa' raised external' thread adj'acent', but spaced from,v

thelatter end'of the rod section, which 'ist-he trated v'full jsizea I'inch `sticker rod, `the di# ameterr'eferred to is thre'ejfoiuths' o f jan inch; v p

At its upperendeacli rod section 1s formed* wit-lr anf integral box 11 vforY the'reception 'of the lower end of the' next liighenrodsection.' Theflna'xim'nm diameter ofthis box 1s prefpose', Without weakening thero'das anfen-'f tiret'y` lthe maximum diameter should preferf ably be' such that the areav of the box nietal .in Cross-sectionatfthe root of the boxtlireadis,r

ias in the case o l the illustrated construction, `tliesame or siibstantiallythe same v'as that of the remainder of the rod. The bore of the box has a cylindrical form asat 12 from the box mouth down for a distance preferably slightly greater than the normal rod diameter and this cylindrical bore portion has cut or otherwise formed therein from end to end an internal screw thread 13. By making this bore portion slightly longer than the rod d1- ameter the length of the threaded portion is such as to afford a perfect thread on a length of the box equal to or slightly greater than the rod diameter, which will be sufficient to withstand stripping of the thread under tensions up to one sufficient tobreak the rod outside the thread. The length of bore portion 12 for the 1% inch rod is preferably 1%c inches, as shown, and from the inner end of portion 12 the bore is gradually and slightly tapered to form a gradually contracting unthreaded bore portion or chamber 14 preferably having a conical bottom wall 14a the apex of which is a. oint at the rod axis, for the purposes hereinafter set forth. If desired Wall 14*l may be rounded to hemi-spherical or less than hemi-spherical contour. The maximum depth of chamber 14 is preferably made as great as possible with the rod and maximum box diameters used and in the rod size shown is preferably hths of an inch as illustrated.

The gradual enlargement of the external diameter of the rod to form the box preferably starts substantially at thebottom of the box, i. e. about two inches from the upper end of the rod section for the 1% inch rod shown, and the internal and external taper of the box wall are preferably the same above the bottom wall 14L of the box. The threaded and unthreaded portions of the box wall merge substantially at the inner end of thread 13 and said wall portions are of the same or substantially the same thickness except where l the wall is cut by the thread groove, and preferably, also except for a short distance down from the mouth of the box. The exterior of the threaded portion of the box is cylindrical as shown and of constant diameterexcept for a short distance downward from the `box mouth where the wall thickness is reduced by tapering the exterior of the box gradually upward and inward to streamline the box mouth and increase the flexibility of .the joint at the mouth of the box. The maximum external diameter of the box for a 5%: inch rod is preferably 11/8 inches and the external diameter at the box mouth is preferably 1 inch, while the length of the externally tapered mouth portion is preferably about l@ inch. The cross-sectional area of the box metal at all points is thus substantially the same as that of the main cylindrical portion of the rod section and practically identical therewith except at the mouth of the box.

From the foregoing it will be observed that the external and internal form of the box is such that abrupt shoulders or changes of cross-section are eliminated and such that the box end of the rod is streamlined, and is also of much smaller over-all diameter and has much less mass of metal than in the standard forms of sucker rod boxes, but has greater strength.

A short distance below the box 11 the cylindrical rod is pressed into square cross-section,

by a 'suitable forging operation, to form al wrench receiving portion 15. It will be obvious that the cross-sectional area of the rod through the wrench receiving portion 15 is the same, or substantially the same, as that of the main cylindrical portion of the rod section. For the 3A inch rod shown, the portion 15 preferably measures Hgths of an inch over flats and nds of an inch over corners as illustrated, and the lengths of the fiats are about 11/2 inches. It will be noted that the usual abrupt shoulders and collars at both ends of the wrench receiving portion are omitted and that the wrench receiving portion thus formed gradually merges into the cylindrical rod section so that this portion of the rod is streamlined and so formed as to avoid concentration of breaking stresses in the rod at this portion. The rod is formed with a second and identical wrench receiving portion 16 about 21/2 inches above its lower end.

At its lower end each rod section is gradually tapered inward as the end of the rod is approached said tapered portion 17 being preferably slightly longer than the side wall of chamber 14 and terminated in a rounded point 17a of substantial surface area adapted to seat on the conical bottom wall 14a of chamber 14 preferably near the outer edge of the bottom wall, as shown, to afford a substantial abutting end-thrust-taking contact area for taking thrust in coupling the sections and on the down pumping strokes, and a universally rockable step bearing for the lower end of one rod section at the bottom of the box of the next lower rod section, for the purposes hereinafter set forth. Point portion 17a is somewhat less than a hemisphere. For the 1%, inch rod shown the maximum length of the tapered and unthreaded lower end portion of the rod section is preferably 'ygths inches. The degree of taper of this rod portion is preferably identical with that of portion 14 of the box, and the size of said rod portion is su-ch as to afford a slight clearance between its periphery and the side wall of portion 14 ofthe box when the rounded point 171` is seated on the bottom wall 14l1 of chamber portion 14, as shown, the maximum diameter of rod portion 17 for the 3@ inch rod shown being Hfths of an inch.

Between wrench-receiving portion 16 and tapered portion 17, each rod section is formed with an external thread 18 over a portion of I vits length corresponding substantially with or slightly less than the length of the threaded portion of box 11, preferably, for the 5X1 inch rod, for a distance of 7/Sths of an inch. Thread 18 preferably terminates about llth of an inch from the upper end of portion 17 so that it maybe screwed fully into thread 13 without engaging the usual unlinished lor imperfect inner end turn of thread 13. The short cylindrical rod portion-19 is preferably reduced to slightly less than the normal rod diameter to maintain a slight clearance between the same and the turn or turns of imperfect thread on the box. The diameter of portion 19 for the 1%, inch rod is preferably Jf-ths of an inch. It will be observed that the portion 19 substantially merges with thread 18.

The thread 18 may be cut or otherwise formed on the rod and its root diameter is the lsame as the diameter of the main cylindrical portion of the rod, namely 3ths of an inch for the 3g inch rod shown.

From the foregoing, it. will be observed -that the lower portion of each rod section is, also without abrupt shoulders, collars or change of section and is of the same or substantially the same V cross-sectional area throughout its threaded connection with the box of the next lower section as it is through the main body portion thereof.

It will be obvious that the invention is capable of embodiment in the type of sucker rod wherein rod sections are joined by union sections having boxes at both ends separated by a common bottom wall or partition, and in other styles of sucker rods than that shown.

The threads 13 and 18 are complementary threads of constant and equal pitch, and, as shown, are preferably the well known selflocking Dardelet type of screw thread. The crest of the thread 18 and the root of thread 18 make an angle of six degrees with the thread axis or the axes ofthe rod sections, the ribs being much narrower than the grooves, so that the slightly conical locking surfaces of the threads will be forced one across the other while in contact from the free-screwing relation shown in Fig. 8, into the self-locked relation shown in Fig. 2 upon a slight further turning between the rod sections in the coupling operation after point 17a seats against wall 14n and arrests the screwing advance of the upper rod section into the box of the lower rod section. The rod sections are thus securely and automatically locked against accidental unscrewing.

In screwing together the usual sucker rod sections thc coupling force places the threaded pin under severe tension to which in service is added the great tension pull incident to the weight of several thousand feet of rod and oil resistance on the up strokes of the rod. This coupling tension quite frequently stresses the pins to, or substantially to, the

limit of tensile strength, so that little or nothing is left to withstand the service load, and is a serious defect in the present standard rods. It will be observed that one of the several functions of the present joint is that the coupling stress after the parts 14a-17 of the large areav step-bearing are brought into contact compresses the externally threaded end of the rod axially, thereby neutralizing, or partly neutralizing, the stretching stress of the service load and greatly increasing instead of decreasing the factor of safety in this respect. This xis an important feature as the factor of safety with respect to tensile strength infstandardsucke'r rods is extremely small, and necessarily so.

Another important feature of the presentjoint, apa-rt from those heretofore mentioned, is that the enforced tendency to bend in the threaded portions common to existing joints is eliminated and a iiexure point provlded remote from the coupled threads bythe largeV area univers/al rocking step bearing 14a-.17 and the clearance between extension -17 and chamber 14, which throws the bends into the main bodies of the adjacent rod sections so that the entire rod section tends to bow and distribute and absorb the lateral and twisting breaking stresses, thus greatly reducing liability of vrod breakage. This isa radical departure from the past practice in sucker rod manufacture. It is well known that in existing forms of sucker rods the most frequent failures have always been breakage through the threaded portions and accidental unscrewing. The past commercial practice in attempting to eliminate these failures has been to constantly increase the diameter, metal mass and rigidity of the joint relatively to the diameter of the main bodies of the connected rod sections until for a 3/4 inch rod, such as shownand most commonly used, the threaded pin diameter is 1-116 inches and the collar and box diameters 1% inches or 1 5/8 inches, thus doubling, or more than doubling, the outside'diameter of the joint and the metal mass and weight at the joint without solving the problems, and it has been proposed to still further increase these diameters. These rigid and heavy joints with their squarely abutting shoulders not only seriously reduce the oil flow through the tubing, which is most commonly 2 inch tubing, but serve to accentuate the lateral vibrations and twisting stresses and the tensile load and thereby increase the breaking and unscrewing tendencies and the ypumping effort.

The present invention provides a strong sectional rod whose sections will not become accidentally unscrewed; a rod which is of minimum weight per unit of length, and of minimum diameter through the joints, and which is streamlined, so that the tensile breaking load and pumping effort are reduced to a minimum and the oil flow increased to a maximum; and a sectional rod which isofsubstantially uniform strength throughout and so constructed. and assembled that @vibration and liability offbreakage are reduced to a minimum and bending. stresses` .widely distributed and absorbedin the main body por tionsof the rod sections and not concentratedin thethreaded parts of rigidthreaded joints.

gWhatI'claim'isu i f 1.,In afsucker rod comprising two units arranged Vend to end, means for lcoupling-said units'yso as todistribute bending stresses, comprising a pairof screw threads on said units screwed together to provide a screw thread connection between theunits, and two portions of saidunits that extendfromone end of the screw thread connectionand have apair of engaged abutmentl surfaces there'- on, one ofwhich abutment surfacesis-a'segmentof-a sphere lgenerated -about a center-y located .on lthe vaxial line'of the rod -unit' on which it is for1ned, and the second oneof which abutment surfaces is so shaped and coactive -kwith the firstvabutment' surfaceas to maintain itsabutting'lengagement therewith duringrelative `angular movements of said portions ofzthe'units underbending stresses,yone of said portions being radially.

free from and enclosed within the other-p0rtion from the engaged .abutment surfaces -to the. adjacent end of the screw thread connection. f

acterized in that, at eachfrodjoint, one member is provided with an axial borey in which seat 'against which saidl rounded tip vof said.

adjacent memberis abutted. l

A rod comprising membersv separably jointed end to end, wherein each tWo adjacent rod members are `held together, contact eachother, and are normally urged into axial alignment, all solely7 throughf'the engagement between a pair of v coupled screwi threads formed on said members,andithe engagement between .a pair ofabutment surfaces formed'v on said members and engageduentirely around the axial line. of the screw thread cony nection formed by the coupled threads, at

a distance from theadjacent end of the screw thread connection atleast equal to the length of said connection,one ofwhich abutment surfaces is a segment of a sphere whose center is on a linecoincident withthe axial line of the screw thread connection. j

4. A ,'ointed sucker` rod comprisingl two membersdirectly Coupled end toend, one .of

2.. A sucker` rod comprisingimernbers'sepa-` rably jointed end to end, said-rod being charfwhichfmembers has'an axial bore into 'which the second member -extends, said'members being engaged solely through the medium of a pair of: coupled screw threads on the l'members and a pair of engagedv endwisely facing abutment surfaces onl the vmembers, one of whichl 'surfaces -is` spheroidal and the other conoidal; the conoidalfabutment surface beinggenerated about an axis coincident with the axialline of the screw thread of the member on which said'surfacefis formed, and the spheroidall abutment surface' being 'gen\ erated about acenter located'on a line coincident with the `axial line of the'screw thread ofthe member on which said surface is formed,wherebya limited universal flexibility`is yprovided in the rod joint, concentration of rod bending stresses inthe rod jointy is prevented, and the rod members are normally urged into axial alignment.

5; A jointed sucker rod as claimed in'claim 4, wherein said abutment surfaces are spaced from the nearest end of the screw thread connection a distance at least equal to the length of saidconnection and are formed on integral portions of the members that 'are free for limited universal angular-movement therebetween laterally of the axial line of the screw thread-connection 1 i 6. Ajointed sucker rod comprising rod units screwed together end to lend wherein, at each rod joint,ione`unit has an axi al chamber into whichthe other unit extends, which chamber has an internally threadedouter portion and a non-threaded inner portion ter.- minating lin a conoidal end wall tapering abruptly toward the rod vaxis in a direction away from th-e outer end of the chamber, whilethe other. 4unit has an'external thread screwed inthe chamber thread and also has a non-threaded end portion peripherally free from the'non-threaded inner portion 'of the chamber' 'and terminating in a'rounded tip whichl is -a segment of a sphere and is abutted against said conoidal end wall of thechamber, said internal thread having a conoidal crest and vsaid external'thread having a conoidal root, which crestand root `are wedged together and taper toward the thread axis inthe direction of the outerl end of the cham` ber ata slight angle"y to the thread axis, said threads having a-pair of steepengaged sides extending from lthe edges of greater diameter of said wedged crest and root, and' I said threads also having suicient'clearance between the other pairof sides therof to unwedging of said crest and root.A

7. A sucker rod comprising a plurality o threaded units screwed directly together end to end,in which each two 'adjacent units are coupled and flexibly held in axial alignment solelyfthrough the medium of the coupled screw threads thereon and two integral portions ofsaid units extending from one end ofthe screw'thread connection, which unit 120 permitportions are adapted for limited anglar movement therebetween laterally of the axis of the screw thread connection in all planes and have a. pair oopposedabutted surfaces thereon adapted for universal. relative wiping movement during 'such' relative angular movements of said portions, whereby localization of bending stresses inthe rod joints is prevented and the jointed rod is madei selfstraightening.

8.` A jointed rod comprising two members arranged end to end and having screw threaded portions screwed together, said members having two non-threaded portions at one end of their screw thread connection, loosely in tertted for limited universal relative angular movement therebetween, one of said non'- threaded portions being an end portion of' one of the members, `,and means on the other member shiftably abutted with said end portion to maintain contact therewith entirely around the rod axis .during relative angular movements of said non-threaded portions and while said portions are axiallyv aligned,

85 whereby rod bending stresses are distributed along said members. Y

9. In a rod comprising a plurality of axially aligned members, means jointing the adja cent end portions of each two adjacent members to avoid localizationv of rod bending stresses in the rod joints, said jointingmeans n for each two adjacent members consisting` solely of a pair of coupled screw threads on i said members and means adapting the mem-v i bers for limited universal relative angular movement about a single center that 1s lo` cated beyond their screwthread connection, said last mentioned means being located at one end of the screw thread connection and 40 being associatedv with said threads to limit v screwing together of said members.v i

In testimony whereof I hereunto ailix my signature; v l

ALFRED MORRIS THOMSON. 

